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71.
72.
Hydrogen production by partial oxidation of methanol (POM) reaction (CH3OH + (1/2)O2 ⇌ 2H2 + CO2) was investigated over a series of CuZnAl ternary oxide catalysts derived from CuZnAl hydroxycarbonate precursors containing
hydrotalcite‐like layered double hydroxide as a major phase. These catalysts exhibited a good catalytic activity and high
H2 selectivity. A methanol conversion of about 40–60% was obtained at 200°C with high selectivity of H2 and CO2. The undesirable by‐product, CO was virtually not produced over most of the catalysts at this temperature. The catalytic
activity was found to decrease with increasing (Cu + Zn)/Al atomic ratio in the precursor and, was correlated with Cu metal
surface areas, Cu dispersion and Cu particle sizes, which were calculated by both XRD and TPR‐N2O passivation methods. The catalyst with higher Cu surface areas and Cu dispersion displayed a higher catalytic activity.
Lifetime experiments showed that these catalysts were stable over a period of 24 h of continuous operation. Catalyst precursors
containing hydroxycarbonates other than LDH as a major phase offered considerable amount of dimethyl ether as a by‐product.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
73.
Conversion of dry gel to microporous crystals in gas phase 总被引:2,自引:0,他引:2
Matsukata Masahiko Ogura Masaru Osaki Takayuki Hari Prasad Rao Poladi Raja Nomura Mikihiro Kikuchi Eiichi 《Topics in Catalysis》1999,9(1-2):77-92
Recently the dry gel conversion (DGC) technique, where a hydrogel is dried and the resultant dry gel is converted into microporous crystals in steam or in a mixed vapor of steam and organic structure-directing agents (SDAs), has been developed. It has been shown that a wide variety of microporous crystals, pure silica microporous crystals, aluminosilicates, metallosilicates, and aluminophosphates, can be synthesized using the DGC method. Remarkable results have been reported in the synthesis of BEA types zeolites, namely aluminosilicate, titaniumsilicate, zincosilicate, and borosilicate with BEA topology, using tetraethylammonium hydroxide, a commercially available SDA. It has also been found that zeolite OU-1, probably analogous to SSZ-31 and NCL-1, is formed via phase transformation from BEA. Dense zeolite coatings like membranes are possible using this method. Characteristics of the DGC method are discussed in detail. This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
74.
Tomonobu Senjyu Yasutaka Ochi Yasuaki Kikunaga Motoki Tokudome Atsushi Yona Endusa Billy Muhando Naomitsu Urasaki Toshihisa Funabashi 《Renewable Energy》2009,34(4):994-999
This paper proposes a technique that determines the optimal windmill operation speed and the optimal rotor flux. Moreover, the position and speed sensor-less wind generation system using the electromotive voltage observer to estimate rotor position and full-order observer to estimate rotor speed and the windmill output torque are proposed. The position and speed sensor-less maximum power point of wind power generation system is controlled by using the above estimated values, optimized windmill operation speed for maximum output power and optimized rotor flux for minimum generator losses. The effectiveness of the position and speed sensor-less maximum power point tracking control for wind power generation system with squirrel cage induction generator is verified by simulations. The simulation results confirm that the proposed method can estimate the operation speed efficiently. 相似文献
75.
This article proposes an extended symmetric diffusion network that is applied to the design of synergetic computers. The state of a synergetic computer is translated to that of order parameters whose dynamics is described by a stochastic differential equation. The order parameter converges to the Boltzmann distribution, under some condition on the drift term, derived by the Fokker-Planck equation. The network can learn the dynamics of the order parameters from a nonlinear potential. This property is necessary to design the coefficient values of the synergetic computer. We propose a searching function for the image processing executed by the synergetic computer. It is shown that the image processing with the searching function is superior to the usual image-associative function of synergetic computation. The proposed network can be related, as a special case, to the discrete-state Boltzmann machine by some transformation. Finally, the extended symmetric diffusion network is applied to the estimation problem of an entire density function, as well as the proposed searching function for the image processing. 相似文献
76.
Gain scheduling control of variable speed WTG under widely varying turbulence loading 总被引:2,自引:0,他引:2
Endusa Billy Muhando Tomonobu Senjyu Naomitsu Urasaki Atsushi Yona Hiroshi Kinjo Toshihisa Funabashi 《Renewable Energy》2007,32(14):2407-2423
Probabilistic paradigms for wind turbine controller design have been gaining attention. Motivation derives from the need to replace outdated empirical-based designs with more physically relevant models. This paper proposes an adaptive controller in the form of a linear quadratic Gaussian (LQG) for control of a stall-regulated, variable speed wind turbine generator (WTG). In the control scheme, the strategy is twofold: maximization of energy captured from the wind and minimization of the damage caused by mechanical fatigue due to variation of torque peaks generated by wind gusts. Estimated aerodynamic torque and rotational speed are used to determine the most favorable control strategy to stabilize the plant at all operating points (OPs). The performance of the proposed controller is compared with the classical proportional-integral-derivative (PID) controller. The LQG is seen to be significantly more efficient especially in the alleviation of high aerodynamic torque variations and hence mechanical stresses on the plant drive train. Simulation results validate the effectiveness of the proposed method. 相似文献
77.
Kentaro Fukuda Noriaki Kawaguchi Sumito IshizuTomohito Nagami Toshihisa SuyamaTakayuki Yanagida Yuui YokotaMartin Nikl Akira Yoshikawa 《Optical Materials》2011,33(6):924-927
Sixty millimeter diameter single crystal of Nd3+ doped LiLuF4 was successfully grown by the Czochralski technique. No remarkable absorption due to unfavorable impurities was observed from optical absorption measurements in the vacuum ultra-violet spectral region. The high crystallinity and homogeneous luminescence characteristics were found from X-ray rocking curve and cathode-ray luminescence respectively. X-ray excited luminescence spectrum was measured and the significant 4f25d-4f3 luminescence at 182 nm was observed in the grown crystal. The pulse height spectrum was taken upon γ-ray irradiation. As a result, the grown crystals demonstrated sufficient response to the γ-ray showing the light yield of 420 ± 30 photons/MeV. The decay curve under α-ray irradiation was also investigated and described by two component decay kinetics which consists of the decay constants of 34 and 450 ns. 相似文献
78.
79.
The determination of the optimal software release schedule plays an important role in supplying sufficiently reliable software
products to actual market or users. In the existing methods, the optimal software release schedule was determined by assuming
the stochastic and/or statistical model called software reliability growth model. In this paper, we propose a new method to
estimate the optimal software release timing which minimizes the relevant cost criterion via artificial neural networks. Recently,
artificial neural networks are actively studied with many practical applications and are applied to assess the software product
reliability. First, we interpret the underlying cost minimization problem as a graphical one and show that it can be reduced
to a simple time series forecasting problem. Secondly, artificial neural networks are used to estimate the fault-detection
time in future. In numerical examples with actual field data, we compare the new method based on the neural networks with
existing parametric methods using some software reliability growth models and illustrate its benefit in terms of predictive
performance. A comprehensive bibliography on the software release problem is presented.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
80.
Hirokazu Osaki Satoshi Miyazaki Yasuhiro Kajihara Yoshiomi Munesawa Hiromitsu Uchiyama 《国际生产研究杂志》2013,51(7):1391-1405
A robot system was developed for the assembly of flexible belt-shaped objects, and the assembly procedures employed by workers in using it were analysed. A multi-fingered hand was developed to hold the objects at several points, and to move them into the proper position for attachment to a part. In addition, an image processing method that can recognize the gripping positions on source objects and conditions after the source objects are attached is proposed. 相似文献